Does anyone have any experience coating magnetic beads with small, bioactive compounds? Specifically, I am trying to coat Invitrogen Dynabeads (Amine or Carboxylic Acid activated) with vitamin B12 (cobalamin) or B1 (thiamine). I am trying to design an assay that will pull vitamin-binding RNA out of a mixed pool of transcripts. However, I have little chemistry background (read: OChem undergrad courses). The activated beads seem simple enough to generate, but I fear that I see it that way because I do not know enough.

For example, the Carboxylic Acid-activated beads are reactive to primary amines following carbodiimide activation. So, I look at thiamine's structure - it has a primary amine - thinking this should link up with the CO2H groups on the beads. With cobalamin, I see a ketone that should react with the amine-activated beads.

Also, I'm considering photoactivatable crosslinkers with less specificity. I would like to have beads with the same vitamin, but with the compound bound in different orientations. Supposedly, the photoactivatable crosslinkers from Invitrogen (eg., ATFB, SE) react with the amine group on the bead and non-specifically with nucleophiles on the ligand. In that case, I assume that I would get some variation in ligand orientation because of the multiple reactive groups (though there may be bias toward some orientations).

If anyone has any experience with this, please let me know. I've searched all over the web for something like this. Maybe I'm not using the right search terms, I don't know. The most relevant I found was a grant award abstract that mentioned using B12-bound beads to purify a riboswitch, but this study is either not complete or has been abandoned.